This invention relates generally to optical systems and elements and more specifically to optically addressable spatial light modulators or light valves.
A spatial light modulator is a class of optical device used for optical computation, switching and displays. A liquid crystal display is one type of spatial light modulator. The liquid crystal display is a two-dimensional spatial light modulator where the physical orientation, and hence magnitude of optical rotation, of a liquid crystal (LC) is modulated by an electric field. In combination with other polarizers in the light path, the intensity of light transmitted through the LC comprising element or light valve is modulated.
Generally, a spatial light modulator includes a modulating write or addressing mechanism. Conventionally, in spatial light modulators, the addressing mechanism is fully electrical, for example, using an active matrix amorphous silicon array to select the voltage at a given pixel""s electrode.
However, optically addressed spatial light modulators are also known. In optically addressed spatial light modulators the voltage across the liquid crystal in the light valve is optically modulated by the exposure of the photoconductor layer to a write beam signal. The write beam is developed externally to the liquid crystal comprising element.
Spatial light modulators also include a read or output mechanism that may be simply the visible observation of the transmitted and modulated light. For a reflective liquid crystal display, the source of light for readout is on the same side of the liquid crystal comprising element. The write mechanism involves a read beam passing through the front side of the liquid crystal comprising element and being reflected back through the front side.
The optically addressed spatial light modulators tend to be bulky. The use of an external write beam takes up excessive space and necessitates optical alignment. Also the optically addressed partial light modulators tend to be expensive and mechanically awkward. Generally, light emitting device arrays are utilized to generate the write beam. These arrays are relatively expensive and not generally monolithic, but rather they are assemblages of large discrete devices.
Thus, there is a need for better ways to implement optically addressed spatial light modulators.